15 September 2011

Soft Tissue Characters Supporting the Great Ape Clades

In my last post, I took a look at some morphological cladistic analyses of hominoids (apes) and tried to compile list of characters that supported the major clades: great apes, African great apes, and mangani (chimpanzees + humans). Unfortunately the studies I looked at only considered skeletal characters (and one of them only craniodental characters). Fortunately, a reader (Dartian) suggested some studies that look at soft tissue characters. I've just skimmed this paper:

The authors compiled a matrix of 171 soft tissue characters and found strong support for the topology produced by earlier molecular studies (gibbons, (orangutans, (gorillas, (humans, chimpanzees)))). Below, I've compiled lists of character states that unambiguously support the major clades:

Great ape synapomorphies (orangutans and African great apes):

Apical lingual gland present in at least some specimens

Most common pattern of insertion of extensor indicis does not involve digit IV (digit II and possibly III only)

Origin of gluteus minimus is discontinuous or variably continuous

Rectus femoris has two heads in at least some specimens

Articularis genus present in at least some specimens

Ratio of nipple position to horizontal height index of nipple position between 1.0 and 1.8

African great ape synapomorphies (gorillas and mangani):

Conical ﬁliform predominate over cylindrical ﬁliform

Radial head of ﬂexor pollicis brevis originates from ﬂexor retinaculum and trapezium only

I was unfamiliar with the term "axillary organ" before today. I looked it up and apparently it's the fancy way of saying "armpit bush". So pungent, hairy armpits are a synapomorphy of African great apes. I had no idea!